The axonal membrane is more permeable to ${\mathrm{Na}}^{+}$ than ${\mathrm{K}}^{+}$ during

The axonal membrane is more permeable to ${\mathrm{Na}}^{+}$ than ${\mathrm{K}}^{+}$ during depolarising phase due to the opening of a large number of voltage-gated ${\mathrm{Na}}^{+}$channels.